As a heat pump which uses vaporization and condensation of a coolant using waste heat, an adsorption heat pump is known. This device employs a method in which vapor of the coolant generated in an evaporator is removed in a form of being captured on an adsorbent, and then, the adsorbent is heated to discharge the captured coolant on a condenser side to again realize a state where the vapor of the coolant can be captured. These processes are repeated to continue to absorb heat (hereinafter called “generate cold heat”) at the evaporator side and to generate heat (hereinafter called “hot heat”) at the condenser side.
Masahiro SUZUKI et al., “Small adsorption refrigerating machine using AQSOA® adsorbent”, Research Papers of Japan Society of Refrigerating and AirConditioning Engineers, 2013 Annual Conference, Sep. 10-12, 2013, pp. 43-44 (hereinafter referred to as “Reference 1”) discloses a capability of a compact adsorption refrigerating machine using the newest zeolite-based water vapor adsorbent and an installation example thereof. According to this reference, a device having an outer size of 1370 mm×1100 mm×750 mm (having a volume of 1130×103 cm3) has a capability of 10 kW.
As a technique closely related to the present invention, it is known that, when a wall surface having a temperature gradient exists in dilute gas, a thermal transpiration flow in one direction along the wall surface is generated from a low-temperature portion on the wall surface toward a high-temperature portion. The dilute gas refers to gas in which, in a certain region, occurrence of collisions between gas molecules is so rare that an equilibrium state is not maintained in the region. Examples of such dilute gas include a case where a gas has a low pressure of about 1 Pa in a region of about 1 cm3, a case where a pressure in a narrow region of a space of 10 nm×10 nm×10 nm is about atmospheric pressure, etc. In a region of a hole size of about 10 nm as in the latter case, the gas becomes dilute gas even at the atmospheric pressure, and the thermal transpiration flow can be generated.
For example, N. K. Gupta et al., “Thermal transpiration in mixed cellulose ester membranes; Enabling miniature, motionless gas pumps”, Microporous and Mesoporous Materials, vol. 142, pp. 535-541, 2011 (hereinafter referred to as “Reference 2”) discloses generation of a thermal transpiration flow under an atmospheric pressure using a porous structure membrane in which many pores having a small pore size of less than or equal to 5 times a mean free path of the medium gas are formed inside the membrane. The mean free path of the air under the atmospheric pressure is about 60 nm. In Reference 2, the medium gas on one surface side of the porous structure membrane is heated with a heater to generate a temperature difference between the one surface of the porous structure membrane and the back surface, to form a temperature gradient in the porous structure membrane, and a thermal transpiration flow is generated from the low-temperature side of the porous structure membrane to the high-temperature side.
In the adsorption heat pump of the related art, it is necessary to provide a switching in time of the cycles of heating and cooling. For this purpose, a plurality of valves and a control device or the like for manipulating the valves are required. Because the valve has a movable part and the movement thereof is controlled, care must be taken for endurance and reliability.